When manufacturing spectacle frames, jewelry, metal parts to be worn on the body or similar items, different criteria have to be met in order to be able to use the product in practice. On the one hand, it is necessary for the manufactured products to be sufficiently strong and, on the other hand, optical demands must be met. The problems of strength arise in particular in the case of spectacle glasses, and there mainly in the rims of the glasses, the hinges or the bows.
Problematic, in particular in the case of spectacle frames, is that they must be soldered once or several times in order to, for example, fasten the hinges or center bridges. The metal softens due to heating so that the alloys must have a high heat resistance so that the spectacle frames remain elastic.
Also for other jewelry, for example brooches, rings, earrings, chains, bands or similar items, it is absolutely necessary that the alloy has, even after the influence of heat, specified strength values in order to avoid mechanical damage during use. Furthermore additional physical characteristics must be met for certain uses, for example with respect to heat conductivity, length expansion coefficient, electrical resistance and electrical conductivity. A further criteria for the selection of such an alloy is its manufacturing ability. The alloy is to be both easily pourable in order to manufacture the necessary blanks, for example, by continuous casting or casting in molds, and also be shapeable in order to be able to produce, for example, rods, wires, bands or similar items from the alloy. Alloys, which partly or fully meet the above-mentioned requirements, are described, for example, in the Gebrauchsmuster 90 17 408.9 or the DE-OS 38 34 186. Also the DE-PS 26 26 251 describes such an alloy. For example, Monel metal has proven to be very good for the above-mentioned uses. Monel metal, however, has nickel contents of approximately 60% to 70%.
The mentioned alloys are distinguished by having a relatively high nickel content. This nickel content is increasingly undesired in jewelry, spectacle frames and other articles, which are worn directly on the skin, since a large number of people have an allergy against nickel. Among others caused by the increasing stress on the environment, the percentage of the population affected by such allergies is on the increase so that nickel-containing alloys are increasingly rejected by the customers. Help comes in some cases from coatings or envelopings, however, this is not possible for most uses. Furthermore, these coatings and envelopings wear off and/or wear at least in certain areas caused by increased use or body contact in those areas.
An alloy for the mentioned purposes is already known from DE-Offenlegungsschrift 41 31 426 A1 (corresponds to U.S. Pat. No. 5,270,001), which alloy does not require the addition of nickel and thereby has a very good mechanical strength and a good corrosion resistance and can be processed in the usual manner. Such an alloy can thus be used in particular for jewelry and to a limited degree also for spectacle frames or similar items without causing nickel allergies to the wearers or users. Additional protective measures, such as, for example, coatings, lacquers or similar measures, with which nickel-containing alloys coming into direct contact with the skin is avoided, are not needed in the finished products. This alloy enables thus a simple, inexpensive manufacturing of the respective products, while, on the other hand, it is also suitable for coatings not containing nickel, for example for decoration purposes, and is distinguished by a good cold-forming property and good elastic characteristics. Also, its processing ability is good. However, a drop in strength occurs during hard-soldering or welding so that the use for spectacle frames is only possible to a limited degree.